The present invention relates to an integrated circuit device, and more particularly to a high blocking voltage integrated circuit device (hereinafter referred to as power IC device) in which a control circuit or driver circuit having a small current capacity and a power semiconductor device having a large current capacity co-exist.
In recent years, demands for the formation of a driver circuit for a motor or solenoid, a power source or the like in a monolithic integrated circuit configuration are remarkable. In such applications, a function of driving a power semiconductor device of a large current (not smaller than 1 A) in a compatible manner with a transistor transistor logic (TTL) is required. As means for satisfying such requirements is a power IC device in which a power semiconductor device and a control circuit or driver circuit for generating a drive signal to control the power semiconductor device is formed in a single semiconductor substrate. Merits of such a power IC device include small size, light weight and low cost owing to high density integration, and improved reliability. However, since there are problems that it is necessary to fabricate a variety of devices in small qualities since different functions are respectively required for the above-mentioned applications and that the current capacity of a power semiconductor device capable of being integrally formed together with a control circuit has a limit under the existing circumstances from the problem of increase in temperatures. In the present state, the generalization of power IC devices is difficult and hence they cannot but be designed every application. As measures to meet the increase of current capacity are considered a method of suppressing the increase of temperatures by reducing the on-resistance of a field effect transistor (MOSFET) used as a power semiconductor device and a method of using a conductivity modulation type FET such as an IGBT (Insulated Gate Bipolar Transistor) the on-resistance of which is small, thereby making it possible to reduce the chip area, as has been disclosed by, for example, Electronic Engineering, July 1987, pp. 48-57. However, the realization of these measures greatly depends on the development of such devices or components.
In the above-mentioned prior art, no consideration is paid to the generality and extensibility of power IC devices. For example, a power semiconductor device to be incorporated in a power IC device must be changed in compliance with the current capacity of a load and hence a variety of devices must be fabricated, whereby resulting in the increase of a cost. Also, there is a problem that a power semiconductor device and a control circuit must be sufficiently distanced from each other as a measure to counter the increase of temperatures, which increases the chip size.